The conservation challenges presented by decorated surfaces are complex for numerous reasons, including the heterogeneous materials used, the variation in size, the different types of decoration, and the intimate link of the decorations to the structures they adorn. The variety of decorated surfaces is as broad as the range of cultures that create them. From prehistoric rock art to ancient Roman mosaics to contemporary street art, we as humans have always had the impulse to embellish, beautify, and give meaning to our built environment.

Decorated surfaces can be two-dimensional, as in mosaics and wall paintings—or three-dimensional, as in sculpted or carved relief and ornamental stucco decoration. They are generally characterized by their size and heterogeneous composition, made with materials that include earth, lime, cement, and gypsum plasters; various paints, glazes, and coatings; and stone and glass tesserae; all applied to a variety of primary supports. The layering of these different materials creates a surface that is often of high quality and refinement, imbued with decorations that contain artistic and technical values, cultural significance, and meaning that may be symbolic, religious, or political. The surface is at the interface between the building and the environment and is particularly vulnerable because it is both exposed to external forces and intimately linked to a building system. Collectively, these characteristics constitute the fundamental conservation challenges for decorated architectural surfaces.

Projects on Decorated Surfaces

In different parts of the world—and at various scales with different objectives—the GCI has conducted projects addressing the conservation issues of wall paintings, archaeological and historic mosaics, and bas-reliefs.

The first GCI field project, initiated in 1986, was the conservation of the thirty-two-hundred-year-old tomb of Queen Nefertari in the Valley of the Queens, conducted with the Egyptian Antiquities Organization (now the Ministry of State for Antiquities); that effort focused on the tomb’s wall paintings. In 1987, the GCI began working with the City of Los Angeles on a challenging project to conserve, protect, and interpret América Tropical, a highly political twentieth-century mural on cement-based plaster by the Mexican muralist David Alfaro Siqueiros. It would be difficult to find two examples of wall paintings so different—from the cultures that made them to the materials and techniques of execution, as well as the conservation issues presented. However, the conservation methodology in both projects was similar, with a strong component of study before intervention. In each case, post-treatment monitoring and maintenance plans were developed and implemented.

The GCI has followed a methodological approach in its projects, in close collaboration with its partners. Projects are developed and interventions planned systematically, in the context of a sound management structure, with interdisciplinary teams comprising professionals from different and complementary specialties. This methodology has ensured a strong scientific approach essential to understanding the materials to be conserved, the environment surrounding the object, and the causes and the mechanisms of deterioration, with the goal of developing and assessing conservation interventions.

A crucial component of GCI field projects on decorated surfaces is scientific research. Material analysis has furthered understanding of original materials and techniques and of agents of deterioration. Conservation of the medieval mosaic on the facade of St. Vitus Cathedral in Prague, begun in the 1990s, is a noteworthy example of a GCI project with a strong scientific component. The glass mosaic adorning the exterior of this highly visited church presented a centuries-old problem of corrosion of the glass tesserae. The main focus of the project, conducted with the Office of the President of the Czech Republic, was the extensive scientific research to develop a protective coating to prevent renewed corrosion of the glass after cleaning.

In addition to field projects with integral scientific components, the GCI has undertaken focused scientific research to tackle specific conservation issues, including evaluation of techniques to identify organic materials in wall paintings, injection grouts for decorated architectural surfaces, backing plasters for detached mosaics, and anti-graffiti coatings for modern murals.

The GCI has also addressed broader issues in the management of sites with decorated surfaces. The close link between site management and decorated surfaces conservation is exemplified by decades-long GCI work at the Mogao Grottoes in China, where appropriate site management has been integrated into the conservation of the wall paintings in the decorated cave temples. The project — a collaboration with the Dunhuang Academy, the stewards of the site — has focused on sustainable visitor and site management in addition to wall paintings conservation.

Education and training have also been emphasized by the GCI, with efforts ranging from integrated training on field projects to developing a university program on the conservation of wall paintings. An early GCI initiative was the creation in 1985 of a degree program in the conservation of wall paintings at the Courtauld Institute of Art, University of London. This program, begun as a partnership, has continued independently and is now a leader in training wall paintings conservators, with fieldwork in Europe and Asia. Today, many Courtauld graduates are practicing conservators and hold prestigious positions in the field.

Training in mosaic conservation has long been a GCI effort, starting with a collaboration with Tunisian authorities—part of the Institute’s mosaics in situ conservation project—begun in 1998 to train conservation technicians to conduct monitoring and maintenance operations. This work evolved into the MOSAIKON initiative, a current GCI partnership with the Getty Foundation, ICCROM (the International Centre for the Study of the Preservation and Restoration of Cultural Property), and ICCM (the International Committee for the Conservation of Mosaics), which aims to improve the conservation, presentation, and management of sites with mosaics through a number of interrelated activities. The initiative has continued the training of conservation technicians and has offered training for decision makers and site managers of archaeological sites with mosaics. It has also sought to strengthen the network of professionals addressing conservation, maintenance, and management of mosaic heritage and to promote the dissemination and exchange of information.

Indeed, dissemination has been an important GCI activity in the conservation of decorated surfaces. The Institute has organized symposia and colloquia and has published proceedings from these meetings, disseminated results of field projects, and made online resources available to conservators. One colloquium specifically addressed the conservation of decorated surfaces on earthen architecture, and another, “Mural Painting and Conservation in the Americas” (co-organized by the GCI and the Getty Research Institute), brought together conservators and allied professionals working on modern murals.

Through research and training, and through the methodological approach taken in its many field projects, the GCI has contributed to the conservation of decorated surfaces. Projects that testify to the efficacy of the methodological approach include the St. Vitus mosaic, Cave 85 at the Mogao Grottoes, polychrome earthen bas-reliefs from the Royal Palaces of Abomey in Benin (1992–97), and América Tropical; currently the tomb of Tutankhamen in Egypt (in partnership with the Ministry of State for Antiquities) and the tablinum of the Casa del Bicentenario in Herculaneum (in partnership with the Herculaneum Conservation Project and La Soprintendenza Speciale per Pompei, Ercolano e Stabia) are examples of the process in practice.

The overall lesson from all of these projects is that a methodological approach to the conservation of decorated surfaces as integral components of the building systems or sites to which they belong is essential to their long-term preservation.

Looking Back, Looking Forward

In the past, the conservation of decorated surfaces was primarily the task of a conservator-restorer or a team of conservator-restorers and technicians. A project would have some scientific support but would likely rely on the knowledge, experience, and judgment of the conservator-restorers. Projects today are more interdisciplinary, and many experts collaborate to characterize materials, study deterioration, design treatments, and conduct monitoring. The projects use an integrated approach: passive and remedial measures are employed not only to treat the architectural and decorated elements, but also to mitigate aggressive environmental conditions and monitor the treatment over time. Treatment is just one component of a project. It is systematically preceded by diagnostic investigations and testing and followed by post-treatment monitoring and maintenance. With contributions by members of a multidisciplinary team, the project is more effective and sustainable.

The evolution of technology has enormously affected the field. Tools used for documentation, scientific investigations, and diagnostic studies have advanced tremendously, and the ease and capacity of data collection and management have improved significantly. Instruments previously confined to the laboratory have become portable and more affordable; they are increasingly available for in situ examination and analysis, allowing conservators to do more for less, and to carry out on-site diagnostic and analytical investigations as noninvasive or minimally invasive operations. Materials analysis has also advanced. The type of information that can be obtained from mere traces of material is impressive, furthering an understanding of the original materials and decoration techniques. Moreover, in situ investigation allows conservators to identify previous intervention materials and assess conditions and treatment options.

A GCI contribution to this research was the Organic Materials in Wall Paintings project (2003–10). Starting from noninvasive and moving to minimally invasive tools, the project, conducted with a number of mostly Italian institutions, developed a methodology for on-site investigation to identify organic materials in wall paintings. The project’s objective was to advance wall paintings conservation by improving methods of identifying organic materials, which are especially vulnerable to interventions, particularly cleaning.

Another critical development has been the establishment of university and other programs that specialize in scientific study and specifically address cultural heritage conservation. The proliferation of such programs has meant that conservator-restorers are increasingly trained in a broad range of conservation topics, and there are now far more professionally trained conservators, scientists, and specialists in cultural heritage preservation who apply their expertise to the complex problems of in situ conservation of decorated surfaces.

Within the GCI, both the scope and the scale of decorated surfaces projects have shifted over thirty years. Early GCI projects focused on single objects, such as the tomb of Nefertari, the Orpheus Mosaic in Cyprus (1988–89), and the bas-reliefs of the Royal Palaces of Abomey. These projects targeted conservation of an individual wall painting, a mosaic, or a set of polychrome earthen bas-reliefs, and the conservation issues were specifically linked to these elements, even if scientific study, post-treatment monitoring, and maintenance were always integral to the project.

As the Institute matures, it is taking an even broader look at decorated surfaces as parts of larger structures or sites and is treating wall paintings in the context of more comprehensive projects. An example is the current conservation of wall paintings in the seventeenth-century church in Kuño Tambo, Peru, which is a component of the GCI’s Seismic Retrofitting Project, whose objective is the design of seismic retrofitting of earthen buildings. Similarly, wall paintings stabilization in the tombs of the Valley of the Queens was but one component of a much larger GCI project with Egyptian officials that addressed conservation issues in the whole valley.

Further Changes

As the field progresses, the additional development of portable tools and instruments will further improve methods for documentation, diagnostic investigation, and in situ treatment evaluation to better identify and mitigate deterioration.

The integrated approach brought to a project by a multidisciplinary team working with committed partners and stakeholders will provide more comprehensive assessments of conditions and conservation options for a site. This, in turn, can reduce the need for large-scale interventions and ensure sustainable conservation solutions for decorated surfaces in the context of the buildings or sites to which they are inextricably linked, thus better preserving the extraordinary variety of decoration embellishing the heritage that surrounds us.

Francesca Piqué, formerly with the GCI, is a professor of science in conservation at the University of Applied Sciences and Arts in Lugano, Switzerland, where she conducts research and teaches the master course in conservation of decorated surfaces. Leslie Rainer, a GCI senior project specialist and wall paintings conservator, is manager of the GCI’s collaborative project to conserve decorated architectural surfaces in the tablinum of the Casa del Bicentenario at Herculaneum.